Scribe line planarization layer

ABSTRACT

An apparatus including a plurality of devices formed on a substrate, and a scribe line area separating each of the plurality of devices, and a masking material overlying a portion of the scribe line area.

[0001] This application is a divisional application of patentapplication Ser. No. 09/541,135, filed Mar. 31, 2000, titled “Method ofForming Scribe Line Planarization Layer.”

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to wafer processing and more particularlyto introducing colorants on a wafer.

[0004] 2. Description of Related Art

[0005] Integrated circuit chips use colorants for a variety ofapplications. One common application is the use of a chip as an imagesensor to capture a color image in a digital imaging system. In oneexample, the image sensor is a semiconductor chip made up of a number ofphotosensitive circuits, each photosensitive circuit capable ofabsorbing light. In color applications, each photosensitive circuitgenerally absorbs light through a color filter that represents aparticular wavelength of light in the visible spectrum corresponding tothe image sensed. The color filter generally contains a colorant, suchas a pigment or dye.

[0006] A CMOS- or CCD-based image sensor is typically formed as a chipor die of a wafer of a number of chips and dies with each chip or dieseparated from one another by a scribe line or scribe line area. Onceformed, the wafer is singulated into individual chips or dies usingconventional wafer dividing tools. The chips or dies are singulated, forexample, by sawing the wafer through the scribe line area.

[0007] In color applications, color filter array (CFA) material isintroduced over a photosensing region or area of the chip or die. CFAmaterial is typically a photoimageable material. The material istypically spin-coated on a wafer, baked, and exposed to ultravioletlight through a mask to crosslink or polymerize the CFA material wheredesired. The remainder of the CFA material is then removed.

[0008] A typical photoimageable CFA material is a two-phase material ofan acrylic resin and an organometallic pigment. For spin-coatingoperations, the CFA material is usually combined into a solution with acasting solvent/dispersing agent to keep the pigment in solution. Thesolution is generally thixotropic in the sense that it has a variableviscosity. The spinning process tends to change this viscosity. There isalso generally a step height between a chip or die and the scribe linearea, such as for example, a step height on the order of five microns(μm). During a spinning operation of CFA material onto a wafer, there isa tendency to form inconsistencies, such as striations or differentcolor patterns (e.g., different color saturation), brought about byphysical forces associated with spinning CFA material in the presence ofa step height. These striations or different color patterns translateinto a systemic noise in the system.

[0009] What is needed is a technique for reducing striations ofcolorants in wafer processing, particularly involving spin-on processesof material containing a colorant.

SUMMARY OF THE INVENTION

[0010] In one aspect, a method is disclosed. The method comprisesintroducing a plurality of integrated circuits on a substrate, eachintegrated circuit separated from another by a scribe line area andintroducing a masking material over a portion of the scribe line area.Following the introduction of the masking material, the method furtherincludes introducing a material comprising a colorant over a portion ofeach of the plurality of integrated circuits and singulating theplurality of integrated circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 shows a schematic top view of a wafer having a plurality ofintegrated circuit devices formed therein/thereon adjacent scribe lineareas.

[0012]FIG. 2 shows a magnified top view of a portion of a wafer of FIG.1 showing an integrated circuit device isolated by scribe line areas.

[0013]FIG. 3 shows a cross-sectional side view of a portion of the waferof FIG. 1 through line A-A, showing a plurality of integrated circuitdevices that are image sensors prior to the introduction of a coloredfilter material over each image sensor.

[0014]FIG. 4 shows the structure of FIG. 3 after the introduction of amasking material and shows the defining of the masking material inaccordance with an embodiment of the invention.

[0015]FIG. 5 shows the structure of FIG. 4 after the definition of themasking material and the scribe line areas of the structure.

[0016]FIG. 6 shows a top view of the structure of FIG. 5.

[0017]FIG. 7 shows the structure of FIG. 6 after the introduction of acolored filter material over the structure and defining the coloredfilter material.

[0018]FIG. 8 shows the structure of FIG. 7 after the definition of thecolored filter material and the singulation of devices.

[0019]FIG. 9 shows a cross-sectional side view of a portion of a waferhaving a plurality of integrated circuit devices formed therein/thereonadjacent scribe line areas and patterned masking material occupying anarea less than the entire area of the scribe line areas in accordancewith a second embodiment of the invention.

[0020]FIG. 10 shows a top view structure of FIG. 9.

[0021]FIG. 11 shows a schematic top view of a portion of a wafer havinga plurality of integrated circuit devices formed therein/thereonadjacent scribe line areas and pattern masking material formed in aportion of the scribe line areas according to a third embodiment of theinvention.

[0022]FIG. 12 shows a schematic top view of a portion of a wafer havinga plurality of integrated circuit devices formed therein/thereonadjacent scribe line areas and pattern masking material formed in aportion of the scribe line areas according to a fourth embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The invention relates to wafer processing and the introduction ofa material comprising a colorant over a substrate of a plurality ofdevices. The invention seeks to minimize, in one aspect, theinconsistency of colorant distribution across an area, such as a sensorarea of an integrated circuit chip. In one aspect, the invention relatesto a method including introducing a plurality of integrated circuits ona substrate, each integrated circuit separated from another by a scribeline area and introducing a masking material over a portion of a scribeline area. A method also includes, after introducing the maskingmaterial, introducing a material comprising a colorant over a portion ofeach of the plurality of integrated circuits and singulating theplurality of integrated circuits.

[0024] The invention also describes an apparatus of a plurality ofdevices (e.g., dies or chips) separated by a scribe line area. A maskingmaterial overlies a portion of the scribe line area. In one aspect, theapparatus is an intermediate structure that may be overcoated with amaterial comprising a colorant by way of a spinning process. Thepresence of the masking material overlying a portion of the scribe linearea minimizes a typical step height between the die or chip and thescribe line area allowing the material comprising the colorant to beintroduced without negative physical forces that may impede the evendistribution of the material, particularly the colorant over theindividual devices.

[0025] The following detailed description describes an embodiment of theinvention involving fabricating image sensors as discrete integratedcircuit devices on a wafer such as a semiconductor wafer. As notedabove, image sensors typically use a CFA material over a photosensingregion or area in color applications. The CFA material typicallyincludes a colorant such as a pigment or dye. It is to be appreciated,however, that various other applications involving introducing amaterial comprising a colorant are contemplated by this invention. Forexample, using a colorant in a photoimageable or other polymer materialas an indicator of curing or polymerization. Accordingly, the inventionis not to be limited to image sensor applications or the introduction ofcolor filter material over a device.

[0026]FIG. 1 shows a typical wafer comprising a plurality of devices(e.g., dies or chips) formed on and/or in the wafer. Wafer 100 is, forexample, a semiconductor wafer such as a silicon wafer. Wafer 100 showsdevices 110 separated from one another scribe line areas 115. Scribeline areas 115 provide a wafer area to singulate devices 110. Scribeline areas 115 may also contain test devices to facilitate testing ofselected one of the plurality of devices 110.

[0027]FIG. 2 shows a magnified view of device 110 on wafer 100. In thisexample, device 110 is an image sensor comprising photosensitive area120 of a plurality of photosensitive circuits. The photosensitivecircuits of an image sensor, often referred to as pixel circuits, aregenerally arranged in an array such as for example 480 rows by 640columns. In general, each photosensitive circuit or pixel circuitcontains a photosensitive element, such as a photodiode, and othercircuitry. The photosensitive element defines photosensing region orarea 120 of the photosensitive circuit that responds to light while thecircuitry, generally speaking, drives a light signal from thephotosensitive region or area to other process circuitry. Typically,device 110 includes column decoders 125 and shift registers 130 and issurrounded at its edges by bond pads 135 that electrically connectdevice 110 to the other components of the imaging system.

[0028]FIG. 3 shows a schematic, cross-sectional side view of a portionof wafer 100 taken through line A-A of FIG. 1. In particular, FIG. 3shows three devices 110 separated from one another by scribe line areas115. At this point, devices 110 are monochromatic in that no CFAmaterial has been introduced over photosensing region or area 120 of thedevices. In the following description, CFA material will be introducedto form image sensors for color applications.

[0029]FIG. 4 shows the structure of FIG. 1 after the introduction ofmasking material 135. In one embodiment, masking material 135 isconformally introduced by known introduction processes, includingspin-coating. Masking material 135 is, in this embodiment, introduced toa step height corresponding to the thickness of devices 110. It is to beappreciated that a different introduction thickness may be used withoutdeparting from the invention. For example, an introduction to athickness smaller than the step height of image sensors 110 may besuitable.

[0030] In one embodiment, masking material 135 is a photoimageablematerial. Masking material 135 is also, in one embodiment, a transparentmaterial. Suitable photoimageable material that is also transparentincludes certain materials having an acrylate moiety including anacrylate polymer of TMR-P7, commercially available from Tokyo Ohka Kogyo(TOK) Company of Japan.

[0031] Following introduction, masking material 135 is subjected to aphoto-definition process. In the example shown in FIG. 4, masking layer135 is introduced over the structure to define opening over scribe lineareas 115. The structure is then exposed to light source 145, such as anultraviolet or other light source. The light source transforms a portionof masking material 135, the exposed portion, and ignores thenon-exposed portion of masking material 135.

[0032]FIG. 5 shows the structure of FIG. 4 after the removal of maskingmaterial 135A in the non-exposed area. Suitable removal techniquesinclude rinsing.

[0033] Following the photo-definition operation, the structure shown inFIG. 5 is cured, for example, by thermal curing operation. In theexample of a TMR-P7 acrylate polymer, one thermal curing operation issubjecting the structure to a temperature of 400° C. for a sufficientperiod of time to cure the polymer.

[0034] As shown in FIG. 5, what remains after the photo-definition andsubsequent processing is masking material 135A with completely filledscribe line areas 115 to a step height equivalent, in this example, tothe step height of devices 110. It is to be appreciated that maskingmaterial 135A need not encompass the entirety of scribe line areas 115but may instead occupy only a portion (e.g., a portion of the width) ofscribe line areas 115. Similarly, masking material 135A need not beintroduced to a step height equivalent to the step height of devices110. One objective in introducing masking material 135A into scribe lineareas 115 is to reduce or minimize the physical forces associated withthe introduction of a subsequent material over the structure. Byintroducing masking material 135A to a thickness similar to the stepheight of devices 110, such physical forces, such as momentum changesbrought about by a spinning process and thickness variations of thestructure may be reduced. FIG. 6 shows a planar top view of thestructure of FIG. 5.

[0035]FIG. 7 shows the structure of FIG. 5 following the introduction ofa material comprising a colorant over the structure. In FIG. 7, CFAmaterial 150 comprising a colorant that is, in one embodiment, a pigmentis introduced over the structure. In one embodiment, prior tointroduction, CFA material 150 comprising a pigment is combined into asolution with a casting solvent/dispersing agent.

[0036] In the embodiment described, CFA material 150 is photoimageable.Accordingly, following the introduction of CFA material 150, CFAmaterial 150 is subjected to a photo-processing operation to transform aportion of CFA material 150. FIG. 7 shows masking layer 155 introducedover the structure to define the areas for photo-definition. FIG. 7 alsoshows the structure being exposed to light source 160, such as anultraviolet light source, to transform a portion of CFA material 150.The photo-definition operation is accomplished by conventionalprocessing techniques.

[0037]FIG. 8 shows the structure of FIG. 7 after the transformation of aportion of CFA material 150 by photo-definition. After thetransformation, CFA material 150 may be cured, such as by a thermaltreatment. Following curing and possibly other processing operations,such as testing of un-singulated devices on wafer 100, the wafer issingulated, for example, by a conventional process. In one example,wafer 110 is singulated in scribe line areas 115 by a sawing process. Inthis example, the singulating process cuts through a portion of maskingmaterial 135A, leaving masking material 135A at the edges of thesingulated devices. It is to be appreciated that, in the examples wheremasking material 135A does not occupy the entirety of scribe line areas115, no masking material 135A may remain after the singulationoperation.

[0038] As described above, scribe line areas 115 are filled with atransparent masking material (masking material 135A), in one embodiment,a transparent material. It is to be appreciated that the maskingmaterial need not cover the entire portion of scribe line areas 115.Instead, the invention contemplates that the masking material may coverless than the entire portion of scribe line areas 115. FIGS. 9-12 showsvarious embodiments of masking material coverage. FIG. 9 is across-sectional side view of a wafer having a plurality of devices 110.FIG. 9 shows devices 110 as, for example, monochromatic image sensors,prior to the introduction of CFA material. FIG. 9 shows masking material135B as lines extending through scribe line areas 115. FIG. 10 shows aplanar top view of this configuration.

[0039] FIGS. 11-12 show still further embodiments of masking materialconfigurations and scribe line areas 115. In FIG. 11, masking material135C is patterned as a plurality of discrete lines through scribe lineareas 115. FIG. 12 shows masking material 135D patterned as chevrons atthe edges of devices 110.

[0040] In the preceding detailed description, the invention is describedwith reference to specific embodiments thereof. It will, however, beevident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

What is claimed is:
 1. An apparatus comprising: a plurality of devicesformed on a substrate; and a scribe line area separating each of theplurality of devices; and a masking material overlying a portion of thescribe line area.
 2. The apparatus of claim 1, wherein the maskingmaterial is transparent.
 3. The apparatus of claim 1, wherein themasking material comprises an acrylate moiety.
 4. The apparatus of claim1, wherein the masking material has a thickness similar to the thicknessof a device portion.
 5. The apparatus of claim 1, wherein the pluralityof devices comprise as one material layer a material comprising one of acolorant.
 6. The apparatus of claim 5, wherein the colorant comprises apigment.
 7. The apparatus of claim 1, wherein the plurality of deviceseach comprise a sensor portion.
 8. The apparatus of claim 1, wherein themasking material overlies the entire portion of the scribe line areaadjacent the plurality of devices.
 9. The apparatus of claim 6, whereinthe masking material comprises a plurality of discrete structuresoccupying less than the entire portion of the scribe line area adjacentthe plurality of devices.
 10. A semiconductor wafer comprising: aplurality of devices formed on the wafer, each integrated circuit mappedon the surface of a wafer adjacent a scribe line area; and a maskingmaterial overlying a portion of the scribe line area.
 11. Thesemiconductor wafer of claim 10, wherein the masking material istransparent.
 12. The semiconductor wafer of claim 10, wherein themasking material has a thickness similar to the thickness of a deviceportion.
 13. The semiconductor wafer of claim 4, wherein the pluralityof integrated circuits comprise as one material layer, a materialcomprising one of a colorant.
 14. The semiconductor wafer of claim 13,wherein the colorant comprises a pigment.
 15. The semiconductor wafer ofclaim 10, wherein the plurality of devices comprise a sensor portion.16. The semiconductor wafer of claim 10, wherein the masking materialoverlies the entire portion of the scribe line area adjacent theplurality of devices.
 17. The semiconductor wafer of claim 10, whereinthe masking material comprises a plurality of discrete structuresoccupying less than the entire portion of the scribe line area adjacentthe plurality of devices.